1. Field of the Invention
The present invention relates to an electronic musical instrument and, more specifically, to an electronic piano which utilizes a microcomputer to detect which keys are being played, the manner in which the keys are being played, and which tab switches have been actuated and to control the sounding of notes in response to the information detected so as to enable the player to produce complex music accurately emulating the sound style of an accomplished pianist.
2. Description of the Prior Art
An electronic musical instrument using continuous tone generators capable of simulating the sounds of a conventional acoustical piano is described in U.S. Pat. No. 4,248,123 issued to Bunger et al., Feb. 3, 1981. The instrument described in the '123 patent includes a gating circuit featuring a switch travel timing circuit having a double-time constant for control of the dynamic range from the keyboard. As noted in the '123 patent, an important element of such instruments involves the electronic circuitry for synthesizing the touch-responsive waveshape envelopes needed to accurately emulate the tonal attack and the decay characteristics of an acoustical piano. The '123 patent discloses the use of a capacitor timing circuit for timing the keyswitch travel to obtain a control potential related to key velocity. The output signal from this circuit was allowed to decay at a double-time constant rate in an effort to provide realistic control over the gating voltages and signal dynamics.
The present invention utilizes a microprocessor to accurately time the keyswitch travel when a key is played. The time measured by the microprocessor is related to a volume level by means of a lookup table stored in a ROM within the microprocessor. The present invention more accurately times keyswitch travel than the capacitor timing circuit described in the '123 patent. In addition, the use of a lookup table containing a value of volume level for each possible travel time within a wide range of travel times provides improved control over the gating voltages and signal dynamics.
The U.S. patent application entitled "Chord Identification System for Electronic Musical Instruments," filed June 18, 1981 by Uetrecht and Simmons, Ser. No. 275,082 and now U.S. Pat. No. 4,389,914 describes a method and apparatus for identifying a chord played on a keyboard of a musical instrument and for identifying the root and the type of chord being played. The apparatus described in the foregoing patent application includes a microprocessor to selectively cause the associated circuitry of the pedal and accompaniment keyboard of the instrument to play automatically either the identified root or a sequence of notes compatible with the identified root and chord. The apparatus described in the foregoing patent application performs the chord identification function through a logical sequence of tests which determine the existence of root intervals, the number of notes, and whether the chord is a major or minor chord. The present invention improves upon the method of identifying chords described in the foregoing patent application. The improvement of the present invention allows for the identification of diminished, augmented, and suspended chords.
In addition, the present invention utilizes microprocessor control in a unique way to provide the playing of automatic style patterns and expanded variations of patterns, which are selectable by tabs operated by the person playing the instrument, and which vary in accordance with the key or keys being played.